The State of the Art and Science of Tree Pruning

Drénou's completely revised, expanded and augmented edition of his unparalleled tree pruning book ? La taille des arbres d'ornement ? is finally available!

This long-awaited update comes as a real treat for the arboriculture community, after a 22-year period of scientific advances and technical progress (1999-2021), between modern and contemporary arboriculture.?

If you have ever fancied studying a second or third language other than English, the time has never felt so right. It's definitely the right time to pick up French and be delighted by every single page from this must-have handbook for tree pruning practitioners of all sorts.

Even though online translators have made enormous progress in recent times, they still translate ? taille ? (pruning) in French as "size". This is how the most complete book of tree pruning worldwide, has been (regrettably) overlooked by the community, except for French- and Spanish-speaking arborists (a Spanish edition was published in 2000).

For instance, in the article appearing in UFUG (ISA's Urban Arboriculture & Urban Forestry), The Research Foundation to Tree Pruning: A Review of the Literature by James R. Clark and Nelda Matheny, 2010, the appendix to the literature review translates Drénou's book as "The size of ornamental trees" instead of "The pruning of amenity trees".?

Drénou, C. 1999. La taille des arbres d’ornement (The size of ornamental trees: how to why). Paris, France: Institut pour le développement forestier (Clark and Matheny, 2010).

Even though online translators outdo themselves nowadays, they still need careful revision to correct the text. As a matter of fact, ? taille ? in French also means "size". It's a homonym just like "bark" in a tree and a "bark" from a dog.

The pruning of amenity trees by Christophe Drénou (2021), gathers authorities like Claire Atger, Yves Caraglio, Dirk Dujesiefken, Claude édelin, Pascal Genoyer, Laurent Larrieu, William Moore, Duncan Slater and Horst Stobbe among other collaborators.

The book comes as a much-awaited support, confirming many discrepancies that we've been carrying for the last two decades, as well as showcasing cutting-edge research and approaches in arboriculture. Its official Facebook page gives a brief overview that I expand here :

We were wrong regarding branch collars as described by Shigo, as well as his overlapping collars hypothesis. Branches without a collar turn out to be the norm, while branches with a collar at the base concern, above all, axes with a loss of vigor, a loss of vitality, shaded axes, declining, senescent or dead.??

The 'D' from CODIT has taken a new dimension. It now stands for 'damage' as a result of desiccation-dysfunction-decay. Woundwood (callus), formerly referred to in French as 'covering callus' is now referred to as 'reinforcing callus', more in alignment to structural reinforcement rather than complete occlusion. Mattheck's Axiom of uniform stress is strongly contested today. Included bark junctions have unveiled a large share of their mystery linked to natural braces. The fork typology proposed by Drénou in 1996, published by Journal of Arboriculture (UFUG), 2000, Pruning Trees: The Problem of Forks, has been refined. Thigmomorphogenesis, the response of plants to mechanical stimuli, has become an essential aspect to understanding trees. Substitute shoots, formerly called suckers, waterspouts or epicormic shoots, turn out to be relevant indicators of tree vitality and solidity.

By far the most relevant contribution of tree architecture as a science and discipline in the last 10 years has been its application in arboriculture. Especially the on-going development of the ARCHI method by Christophe Drénou, closely monitored by Yves Caraglio. It validates scientifically a practical visual architectural diagnosis of the vitality of trees, allowing for a comprehensive reasoned decision-making.?

New techniques have emerged regarding tree support systems, either static or dynamic. Daring not to prune, once perceived as negligence, is now considered a modern full-fledged management method allowing trees complete freedom to express their natural form; to live a long time; to constantly consolidate facing winds; to rebuild after disorganization; to do ground layering; to carry dead branches; to participate in the cycle of life; to meet societal expectations. Dendromicrohabitats, largely responsible for biodiversity on the planet, must be taken into account in the same way as the living, sensitive and fragile identity of trees.

For quite a while, we've believed that roots, the hidden side of plants, were our weakest point regarding our quest to understand trees. In reality, we know much more today. The most abstract dimension of trees is time. Tree time is lengthy and we have to learn to wait, observe, anticipate and plan. Trees belong to a biological clock entirely different from ours. If our management is synchronized with their time, we understand that the potential risk that they represent for our safety is temporary. A tree has the potential to reconstruct itself over time if it has sufficient vitality with vigorous substitute shoots.

(Taken from Drénou's ? La taille des arbres d'ornement ? official Facebook page)

"How a tree responds to pruning and then regenerates is extraordinarily variable. There are many diverse factors capable of modifying this response.

Architectural resilience parameters after pruning (in a non-restrictive environment):

The tree before pruning:

? The species (Architecture-CODIT)

? Age (young-adult-mature-senescent)

? State (healthy-stressed-resilient-declining)

? Status (individual-colony)

? Form (natural-pruned)

Pruned axes:

? Vitality (living-dying-dead)

? Function (branch-substitute shoot)

? Ramification (normal-impoverished)

? Axis categories (C1-C2-C3-C4)

? The nature of forks

Pruning:

? Intensity

? Frequency

? Distribution?

? Quality

? Seasons"

Drénou's much awaited tree pruning book, set on the principle that pruning should not be systematic but rather the result of a methodical approach, proposes reasoning adapted to a wide variety of cases encountered in the field. Extensively illustrated with photos and technical drawings, it comes with 34 concrete tree pruning case studies, integrating cutting edge research in tree architecture and tree anatomy (CNPF, 2021).?

Christophe Drénou, PhD in tree architecture, comes from the "Montpellier school". Disciple of Claude édelin, indisputable authority on tree architecture, from the Mecca of French botanists generated by Francis Hallé. His doctoral thesis on the senescence of trees directed by édelin and his ongoing development of the ARCHI methodology (Architectural diagnosis of the vitality of trees), closely monitored by Yves Caraglio, place Drénou as an authority at the summit of arboriculture. Author/Editor of the most complete book on tree pruning available ? La taille des arbres d'ornement ?. Author/Editor of the most complete book on tree roots available, ? Les racines : face caché des arbres ? (Roots: The Hidden Side of Trees) and author of ? Face aux arbres : Apprendre à les observer pour les comprendre ? (Facing Trees : Learning to Observe Them in Order to Understand Them), the most comprehensible handbook to understanding trees available.??

References:

CNPF, 2021. la taille des arbres d'ornement (2e édition) Architecture - Anatomie - Techniques. https://www.foretpriveefrancaise.com/publications/voir/370/la-taille-des-arbres-d-ornement-2e-edition/n:541

Drénou, C., 2021. La taille des arbres d’ornement : Architecture - Anatomie - Techniques (2e édition). CNPF, Institut pour le développement forestier.

Drénou, C., 2021. La taille des arbres d'ornement. Facebook page. https://www.facebook.com/faceauxarbres/

David S. Restrepo, Paris, 2021.09.05

v. 1.0.1.2021.09.05